The photovoltaic air-conditioning system with grid-connecting and inverting functions in the prior art is shown in FIG. 1, which is configured to make it convenient for the photovoltaic battery to supply power for a main circuit of an air conditioner, and to have a simple circuit easily implemented. Take a single-phase grid-connected system as an example, when the photovoltaic battery is electrically connected to the photovoltaic air-conditioning system, the electric energy is transferred to the grid-connected inverter circuit and the compressor inverter of the air conditioning system through the voltage boost circuit and direct current (DC) buses. The grid-connected inverter circuit feeds the electric energy of the photovoltaic battery to the power grid. The compressor inverter of the air conditioning system converts direct current in the DC buses to alternating current (AC) which is required for speed adjusting of the compressor, so as to drive the compressor to operate.
When the compressor of the air conditioner is driven to operate by electric energy from the power grid, the rectification and PFC (Power Factor Correction) circuit converts AC output from the power grid to DC, and ensures the electric energy input from the power grid to have a constant unity-power factor. When the grid-connected inverter circuit performs grid-connecting and inverting, rectification is not performed, so that the rectification and PFC circuit doesn't work and no electric energy is input from the power grid. When the grid-connected inverter circuit doesn't perform grid-connecting and inverting, the rectification and PFC circuit inputs electric energy from the power grid and drives the compressor of the air conditioner to operate.
With the photovoltaic air-conditioning system above, it is realized to supply power for the main circuit of the air conditioner by the photovoltaic battery. However, when grid-connecting and inverting are performed, the down bus of the DC buses is still connected to the live wire and the neutral wire of the power grid through the rectification bridge, which will easily cause the grid-connected inverter current to flow into the down bus through the rectification bridge, and thus interfering with normal control of the grid-connected inverter current.